A guide to soundbar connections: ARC, eARC, Toslink
Slim TVs produce lacklustre sound. The solution? A soundbar. But which connection gives you the best sound? Here’s a rundown of all the soundbar connections and their pitfalls.
The World Cup is just around the corner. And once that first starting whistle blows, plenty of viewers are going to be hit with a realisation. Namely, that although their TV produces a crystal-clear picture, the sound is about as captivating as a post-match press conference following a 0–0 draw. Given how thin modern TVs are becoming, this is hardly surprising. On an ultra-slim set, there’s very little room for decent speakers. The most obvious solution to this is a soundbar.
Before you buy one, however, you’ll need to check the back of your TV. The question is: which audio connections does your TV actually support? HDMI? With ARC? With eARC? Optical? Bluetooth? And which connections do what? This article explains all the relevant connections between your TV and soundbar, their history, their technical characteristics and their pros and cons.
HDMI ARC and eARC: the modern standard solution
If you’re buying a TV and a soundbar today, look out for the letters «ARC» or «eARC». ARC (Audio Return Channel) was introduced alongside HDMI 1.4 in 2009, making it possible for an HDMI cable to transmit audio signals in both directions for the first time. As a result, instead of using an optical or coaxial cable to connect a TV to a soundbar, all that’s needed is a second HDMI cable. On the flipside, ARC doesn’t cut it when it comes to high-end audio formats like Dolby Atmos or uncompressed multichannel audio – its bandwidth is too low for them.
Source: Florian Bodoky
With precisely this in mind, the HDMI Forum launched eARC, the successor technology, alongside HDMI 2.1 in 2017. The extra «e» stands for «enhanced», which basically sums up its entire purpose: more bandwidth. Thirty-seven Mbit/s more, to be exact. With eARC, virtually all of the latest audio formats can be transmitted, including Dolby TrueHD, DTS-HD Master Audio, Dolby Atmos and DTS:X. It doesn’t even have trouble with uncompressed multichannel audio with up to eight channels.
This really comes to the fore if you’re watching high-production-value films or 4K content. While ARC struggles with complex audio formats, eARC transmits data without any loss. Plus, it comes with features such as automatic device detection and volume control via the TV remote. Mind you, both your TV and soundbar need to support eARC for that to work. Provided your TV does, you’d be hard-pressed to find a better solution than eARC.
To find out if your TV supports eARC, simply check the HDMI ports. If they’re labelled «ARC» or «eARC», you’re good to go. The product description of your chosen soundbar will tell you whether its HDMI port supports ARC or eARC.
HDMI without ARC: the historical exception
Not every HDMI port is an ARC port – a fact that still causes confusion to this day. Owners of older TVs in particular might see several HDMI ports on the back of their device, and yet find that their soundbar won’t work with their chosen connection.
HDMI was the first technology to transmit both video and audio digitally to a TV via a single connection. However, back when the HDMI standard was introduced in 2002, no one had thought of an HDMI-based return channel for audio yet. Consequently, even though the TV can receive audio from a connected source, it can’t transmit it to the soundbar via HDMI. If that’s the case, you’ll need a soundbar that can also be connected via an optical or coaxial audio port.
Optical (Toslink): the red light from the 1990s
If you have an older TV with HDMI but without ARC support, you’re probably already familiar with the alternative. Yep, that little square port on the back of your TV with a red light shining from it: Toslink.
Developed by Toshiba in the early 1980s, Toslink was considered the standard for digital audio connections in home cinema systems for decades. While other connections transmit electrical signals, Toslink uses light pulses. This makes the connection unsusceptible to electromagnetic interference and prevents common issues such as ground loops.
In the 1990s and 2000s, optical connectors were practically everywhere. TVs, DVD players, AV receivers and home cinema systems often communicated with each other through this interface. It wasn’t until the rise of HDMI that it started losing its significance. Technically speaking, however, Toslink still delivers solid performance. It’s more than good enough for conventional TV, fine for stereo or compressed surround. The system’s limitations only become evident with HD audio formats. Dolby TrueHD, DTS-HD Master Audio and lossless Dolby Atmos require much more bandwidth than the optical standard can provide (around 384 kbit/s).
S/PDIF (coaxial): the evergreen
Source: Galaxus
The coaxial connection uses a 75-ohm cable with RCA connectors. The signal is transmitted electronically, allowing for cable lengths of several metres without any significant loss of quality.
This standard supports the transmission of PCM audio with up to 24-bit resolution and sampling rates of up to 192 kHz. In addition, compressed multichannel formats such as Dolby Digital and DTS can be transmitted as a bitstream. This made the coaxial cable a popular interface for home cinema systems and AV receivers for many years.
However, its bandwidth is limited. Contemporary high-resolution multichannel formats such as Dolby TrueHD, DTS-HD Master Audio or object-based formats such as Dolby Atmos can’t be fully transmitted. Even so, coaxial cables are still widely used. The technology is considered robust and reliable, providing a simple way to exchange digital audio signals between compatible devices.
Analogue: the forgotten brother
Source: Galaxus
Before digital interfaces made their way into living rooms, sound was transmitted exclusively in analogue form. The best-known examples of this generation are red and white RCA jacks (and, of course, 3.5 mm jack plugs). These connections transmit audio signals as electrical currents. For decades, this was the standard for virtually all audio applications. From Walkmans to stereo systems to tube TVs, almost everything was based on analogue technology.
Viewed through a modern lens, however, it has an obvious drawback. Analogue connections typically only transmit stereo sound. As a result, modern surround-sound formats and lossless multichannel formats aren’t supported. What’s more, analogue signals are susceptible to interference and loss of quality. That being said, these connections still have a place in today’s audio landscape. If there’s absolutely no digital alternative available – say, on a secondhand AV receiver – analogue cables often still deliver better sound than the built-in speakers on many TVs.
Bluetooth: wireless convenience
Bluetooth has become one of the most ubiquitous technologies in our day-to-day lives. Headphones, smartphones, speakers and smartwatches have been communicating wirelessly for a long time now. So it’s little wonder that TVs and soundbars often support Bluetooth as well. The technology was developed in the late 1990s and originally had one main goal: to replace cables. Which is exactly why Bluetooth is still so appealing. Setting it up usually takes just a few seconds, you don’t need any additional cables and you can place the soundbar wherever you want.
However, this convenience comes at a price. Since Bluetooth compresses audio signals, it isn’t designed for maximum sound quality. Despite the availability of modern codecs such as aptX HD and LDAC, which deliver significantly better results, many TVs still rely on basic codecs like SBC. Which brings us to another problem: latency. If audio is transmitted with a delay, the TV’s picture and sound might fall out of sync. Though barely noticeable during a podcast, it’d definitely be obvious during the World Cup final. Just imagine the commentator shouting «Goal!» before the ball has even hit the net.
Wi-Fi and network audio
The latest audio transmission trend is a shift away from direct connections and towards home networks. Modern soundbars from manufacturers such as Sonos, Bose, Samsung and LG often feature Wi-Fi capabilities and can stream music straight from a network. The major advantage of this? You can easily stream music from smartphones, tablets or computers without a single audio cable.
However, this isn’t yet well established in the arena of TV audio. This is down to the synchronisation between the picture and sound. Even the slightest delays can be discombobulating. That’s why most manufacturers continue to rely on HDMI eARC for connecting TVs to soundbars. Wi-Fi, on the other hand, is mostly used for music streaming and multi-room systems. This makes network audio an addition to – but rarely a complete replacement for – a wired TV connection.
Verdict: which connection should you choose?
Ultimately, the right connection for you will largely depend on how old your devices are. If both your TV and soundbar support eARC (which even very cheap TVs do these days), you won’t need to think twice about the connection. No other interface gives you a comparable combination of sound quality, convenience and future-proofing. It supports all modern audio formats, the system’s easily controlled via a TV remote and transmits even complex audio tracks to the soundbar without any loss of quality.
Don’t have an HDMI eARC port? Don’t worry. ARC is still an excellent everyday solution – it’s perfectly adequate for most uses.
If there’s no available HDMI return channel feature, an optical connection is your best bet. While you won’t have access to some modern audio formats, the bandwidth is more than good enough for multichannel audio and reliable playback. Bluetooth, on the other hand, is especially appealing because it eliminates cable clutter. However, it’s a makeshift solution. You also need to put up with a few trade-offs when it comes to sound quality, stability and latency. Finally, analogue connections are mainly a stopgap solution for older devices.
I've been tinkering with digital networks ever since I found out how to activate both telephone channels on the ISDN card for greater bandwidth. As for the analogue variety, I've been doing that since I learned to talk. Though Winterthur is my adoptive home city, my heart still bleeds red and blue.
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